Projector and control method therefor

ABSTRACT

Disclosed herein is a projector for projecting an image to a screen, including: a lamp configured to emit light; an elliptic reflecting mirror configured to reflect and condense the light from the lamp; a sensor configured to detect the amount of the light reflected and condensed by the elliptic reflecting mirror; a lamp power supply configured to supply power to the lamp to drive the lamp; and a control circuit configured to successively increase the power to be supplied from the lamp power supply to the lamp until after a variation value of the amount of the reflected light detected by the sensor becomes equal to or lower than a predetermined threshold value.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2007-060440 filed in the Japan Patent Office on Mar. 9,2007, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a projector and a control method therefor, andmore particularly to a projector and a control method therefor suitablefor use where light is emitted from a lamp.

2. Description of the Related Art

In recent years, together with development of the image displaytechnique, a projector which can be applied to the field of digitalcinemas, that is, a projector which can be used for applications ofscreening of a movie in a movie theater, has appeared. One of projectorsof the type described is disclosed, for example, in Japanese PatentLaid-Open No. Hei 5-260423.

SUMMARY OF THE INVENTION

In an existing projector, if a flicker phenomenon, that is, flickeringof a screen image, occurs, then either the lamp is exchanged or theinput power to the lamp is increased so that the luminance of the lampbecomes equal to or higher than a preset value. However, the existingprojector has a problem in that the life of the lamp upon low inputpower driving when a flicker phenomenon occurs may not be assuredsufficiently.

Therefore, it is demanded to provide a projector and a control methodtherefor by which a flicker which occurs upon low input power driving issuppressed so that a sufficient lamp life can be assured upon low inputpower driving.

According to an embodiment of the present invention, there is provided aprojector for projecting an image to a screen, including a lampconfigured to emit light, an elliptic reflecting mirror configured toreflect and condense the light from the lamp, a sensor configured todetect the amount of the light reflected and condensed by the ellipticreflecting mirror, a lamp power supply configured to supply power to thelamp to drive the lamp, and a control circuit configured to successivelyincrease the power to be supplied from the lamp power supply to the lampuntil after a variation value of the amount of the reflected lightdetected by the sensor becomes equal to or lower than a predeterminedthreshold value.

The projector may further include a position adjustment mechanismconfigured to adjust the position of the lamp so that the bright pointof the lamp is displaced from a first focus of the elliptic reflectingmirror. In this instance, the projector may be configured such that theposition adjustment mechanism adjusts the position of the lamp when theaspect ratio of the image displayed on the screen changes. Or, theprojector may be configured such that the position adjustment mechanismmoves the bright point of the lamp along an optical axis of the ellipticreflecting mirror or along a direction different from the optical axis.

The projector may further include a display section configured todisplay an alarm for urging for exchange of the lamp when the variationvalue exceeds the predetermined value while the power supplied from thelamp power supply to the lamp has a maximum value.

The threshold value may be a specified value determined in advance.

According to a different embodiment of the present invention, there isprovided a control method for the projector described above. Inparticular, according to the different embodiment of the presentinvention, there is provided a control method for a projector forprojecting an image to a screen, the projector including a lampconfigured to emit light, an elliptic reflecting mirror configured toreflect and condense the light from the lamp, a sensor configured todetect the amount of the light reflected and condensed by the ellipticreflecting mirror, a lamp power supply configured to supply power to thelamp to drive the lamp, and a control circuit configured to control thelamp power supply, the control method including the step, executed bythe control circuit, of successively increasing the power to be suppliedfrom the lamp power supply to the lamp until after a variation value ofthe amount of the reflected light detected by the sensor becomes equalto or lower than a predetermined threshold value.

With the projector and the control method for a projector, the life ofthe lamp can be extended. Particularly, it is possible to sufficientlyassure the life of the lamp upon low input power driving when a flickerphenomenon occurs thereby to extend the life of the lamp.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of a configuration of aninformation processing system applied to the field of digital cinemas;

FIG. 2 is a schematic view illustrating a vista size and a scope size;

FIG. 3 is a diagrammatic view illustrating adjustment ranges of thelight amount of lamps;

FIG. 4 is a block diagram view showing a projector to which the presentinvention is applied;

FIG. 5 is a schematic view showing an internal configuration of a lamphouse on which a lamp is mounted;

FIG. 6 is a schematic view showing an appearance of the lamp;

FIG. 7 is a diagrammatic view illustrating a manner of reflection oflight by an elliptic reflecting mirror with respect to the position of alight source;

FIG. 8 is a graph illustrating the amount of movement of the lamp andthe relative illuminance on different axes;

FIG. 9 is a block diagram showing a detailed configuration of the lamphouse;

FIG. 10 is a flow chart illustrating a flicker detection process; and

FIG. 11 is a flow chart illustrating a lamp position adjustment process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Before a preferred embodiment of the present invention is described indetail, a corresponding relationship between several features recited inthe accompanying claims and particular elements of the preferredembodiment described below is described. The description, however, ismerely for the confirmation that the particular elements which supportthe invention as recited in the claims are disclosed in the descriptionof the embodiment of the present invention. Accordingly, even if someparticular element which is recited in description of the embodiment isnot recited as one of the features in the following description, thisdoes not signify that the particular element does not correspond to thefeature. On the contrary, even if some particular element is recited asan element corresponding to one of the features, this does not signifythat the element does not correspond to any other feature than theelement.

According to an embodiment of the present invention, there is provided aprojector (for example, a projector 33 shown in FIG. 4 which can beinstalled in movie theaters 11A to 11N shown in FIG. 1) for projectingan image to a screen (for example, a screen 34 shown in FIG. 1),including a lamp (for example, a lamp 83 shown in FIG. 4 which has ashape shown in FIG. 6) configured to emit light, an elliptic reflectingmirror (for example, an elliptic reflecting mirror 82 shown in FIG. 4)configured to reflect and condense the light from the lamp, a sensor(for example, a light amount sensor 60 shown in FIG. 4) configured todetect the amount of the light reflected and condensed by the ellipticreflecting mirror, a lamp power supply (for example, a power supplysection 59 shown in FIG. 4) configured to supply power to the lamp todrive the lamp, and a control circuit (for example, a CPU 51 shown inFIG. 4) configured to successively increase the power to be suppliedfrom the lamp power supply to the lamp until after a variation value ofthe amount of the reflected light detected by the sensor becomes equalto or lower than a predetermined threshold value.

The projector may further include a position adjustment mechanism (forexample, the lamp position adjustment mechanism 91 composed of the CPU51, an I/O section 54, a motor drive 55, an encoder 56, a motor 57, anelectric power section 81 and so forth shown in FIG. 4) configured toadjust the position of the lamp so that the bright point of the lamp isdisplaced from a first focus of the elliptic reflecting mirror.

In this instance, the projector may be configured such that the positionadjustment mechanism adjusts the position of the lamp when the aspectratio of the image displayed on the screen changes (for example, a lampposition adjustment process of FIG. 11).

Or, the projector may be configured such that the position adjustmentmechanism moves the bright point of the lamp along an optical axis ofthe elliptic reflecting mirror or along a direction different from theoptical axis (for example, a process at step S34 of FIG. 11).

The projector may further include a display section (for example, adisplay section 72 shown in FIG. 4) configured to display an alarm forurging for exchange of the lamp when the variation value exceeds thepredetermined value while the power supplied from the lamp power supplyto the lamp has a maximum value.

According to a different embodiment of the present invention, there isprovided a control method for the control circuit of the projectordescribed above (for example, a method corresponding to a flickerdetection process of FIG. 10 from among processes executed by the CPU 51of the projector 33 of FIG. 4).

In the following, a preferred embodiment of the present invention isdescribed with reference to the accompanying drawings.

FIG. 1 shows an example of a configuration of an information processingsystem to which the present invention is applied wherein it is appliedto the field of digital cinemas.

Referring to FIG. 1, the information processing system shown includesvarious apparatus hereinafter described which are installed in movietheaters 11A to 11N and a maintenance server 12 connected to each otherby a predetermined network 13 such as the Internet. The maintenanceserver 12 here is an apparatus used by a person who provides maintenanceof the apparatus installed in the movie theaters 11A to 11N as aservice.

The movie theater 11A includes a plurality of screening places 22 a to22 n so that a plurality of movies can be shown concurrently. In orderto collectively manage the screening places 22 a to 22 n, a theatermanagement (TM) apparatus 21 is installed in the movie theater 11A.

Further, a screen management (SM) apparatus 31 a, a material server 32a, a projector 33 a and a screen 34 a are provided in the screeningplace 22 a.

Similarly, a screen management apparatus 31 n, a material server 32 n, aprojector 33 n and a screen 34 n are provided in the screening place 22n. Also any other screening place 22 k not shown includes a screenmanagement apparatus 31 k, a material server 32 k, a projector 33 k anda screen 34 k not shown. Here, k is an alphabet of a small letterbetween a and n.

It is to be noted that, in the following description, where there is nonecessity to individually distinguish the screening places 22 a to 22 nfrom one other, any of them is referred to simply as screening place 22.Further, where the screening place 22 k is referred to simply asscreening place 22, also the screen management apparatus 31 k, materialserver 32 k, projector 33 k and screen 34 k are individually referred toas screen management apparatus 31, material server 32, projector 33 andscreen 34, respectively.

The screen management apparatus 31 carries out management of the entirescreening place 22 and controls the other apparatus in the screeningplace 22, that is, the material server 32, projector 33 and so forth.Further, the screen management apparatus 31 communicates with thetheater management apparatus 21 to supply and receive variousinformation to and from the theater management apparatus 21.

The material server 32 provides digital data of a movie or material tobe screened in the screening place 22 to the projector 33.

The projector 33 projects an image corresponding to the digital datasupplied thereto from the material server 32 to the screen 34. The movieis screened on the screen 34 thereby.

Also the other movie theaters 11B to 11N have one or more screeningplaces 22, in each of which a screen management apparatus 31, a materialserver 32, a projector 33 and a screen 34 are provided.

The information processing system of FIG. 1 is applied to the field ofdigital cinemas as described hereinabove. In the field of digitalcinemas, standards called DCI Spec are defined by an organization calledDCI (Digital Cinema Initiatives). According to the standards, it iswritten expressly that, as an image parameter to be referred to, “Thewhite peak luminance should be 48 cd/m² (14 ft-L) at the center of thescreen.” Since 14 ft-L=48 cd/m², a brightness provided by approximately48 candles is demanded per 1 m² at the center of the screen 34. In otherwords, it is necessary to normally keep the luminance or brightness ofan image projected on the screen 34 fixed.

On the other hand, the screen 34 may have a size selected from amongvarious types of size depending upon the volume of the screening place22 and so forth.

Therefore, it is necessary to adopt, as a light source of the projector33, an optimum lamp which can satisfy the DCT Spec such as, for example,a xenon lamp in accordance with the size of the screen 34 of an objectof projection.

Also as regards the angle of field for a movie, various types which aredifferent in aspect ratio such as, for example, scope and Vista areavailable. Accordingly, it sometimes becomes necessary to change overthe angle of field for use in the same screening place 22, that is, foruse on the same screen 34, from one to another one of the various anglesof field. In this instance, it is necessary to change the magnificationin zooming of the lens of the projector 33. Further, it is necessary tochange the power or input watt of the lamp in response to the change ofthe zooming magnification in order that the luminance or brightness ofan image on the screen 34 may be kept fixed as described hereinabove. Asa result, it is necessary to assure the light amount gain of the lamp ata fixed amount.

Referring to FIG. 2, the vista size is a horizontally elongated screensize having an aspect ratio of approximately 1:1.66, in the example ofFIG. 2, an aspect ratio of approximately 1:1.85. As a representative oneof such vista sizes, a vista size of 1:1.66 (European standards),another vista size of 1:1.85 (U.S. standards) and so forth areavailable. Meanwhile, the scope size is a horizontally elongated screensize having an aspect ratio of 1:2 or more, in the example of FIG. 2, anaspect ratio of 1:2.39. As a representative one of such scope sizes, thecinema scope size (registered trademark) having an aspect ratio of1:2.35 and so forth are available.

Since the scope size is obtained, for example, by multiplying the vistasize by 1.26 in both of the vertical direction and horizontal direction,the scope size has a magnitude equal to 1.6 times (≈1.26×1.26) the vistasize. Accordingly, upon changeover from the vista size to the scopesize, if the lamp power is increased to 1.6 times, then the luminanceper unit area becomes fixed. For example, if the lamp power for thevista size is 50%, then 1.6 times the lamp power, that is, 80%, arerequisite as the lamp power for the scope size. It is to be noted that,although upper and lower portions of the screen of the scope sizeindicated by slanting lines are not observable as seen in FIG. 2, asviewed from the lamp side, power including that for the slanting lineportions is requisite.

Further, since it is necessary to keep the luminance or brightness of animage on the screen 34 fixed as described hereinabove, it is necessaryto adopt a lamp which can cope with a change in power in terms ofminimum watt and maximum watt as input ratings (such input ratings arehereinafter referred to as lamp size) and to carry out suitable settingalso on the driving side for the lamp. In other words, there is theprobability that the projector 33 may incorporate lamps of various lampsizes.

For example, such three different lamps as seen in FIG. 3 areincorporated in the projector 33. Referring to FIG. 3, the lamp A isdriven within a range between minimum watt of 2.1 kW and maximum watt of2.4 kW. Similarly, the lamp B is driven within another range betweenminimum watt of 1.5 kW and maximum watt of 3.0 kW, and the lamp C isdriven within a further range between minimum watt of 1.0 kW and maximumwatt of 2.0 kW.

In particular, since a lamp is mounted on a predetermined lamp house, inthe present embodiment, in a lamp house 58 shown in FIG. 4, the threelamps mentioned hereinabove have a same or similar shape in order toassure a function, for example, in the present embodiment, have such ashape as seen in FIG. 6. No particular prescriptions are available forthe lamp size, and there is the possibility that lamps of various lampsizes may be circulated on the market. Particularly in such a case thatthe movie theaters 11A to 11N are located discretely at remotedistances, lamps of lamp manufactures or makers in the districts areadopted frequently. In such an instance, lamps of various lamp sizesdifferent in different districts may be distributed on the market withhigher possibility. Accordingly, even if the projector 33 projects animage to the screen 34 of the same size, lamps of different lamp sizesare adopted as the lamp to be incorporated in the movie theaters 11A to11N.

In this manner, the lamp for use with a projector in the field ofdigital cinemas involves a situation unique to the field. As a result, amovie theater in which an existing projector is used suffers from suchvarious problems as described below.

For example, even if changeover between the scope size and the vistasize is carried out, it is necessary to always keep the luminance orbrightness of an image projected on the screen 34 fixed. In thisinstance, in order to assure a fixed luminance, for example, it isnecessary to assure the light amount gain of the lamp at 1.6 asdescribed hereinabove. However, since only 2.0 (50% to 100%) isavailable as the input gain of a lamp in the past, it is necessary tonormally use low input power, and therefore, there is a problem that asufficient life has to be assured even where the input power is low.Further, a flicker phenomenon has a nature that it begins with low inputpower and ends if the power of the lamp is raised. For example, theflicker phenomenon begins with lower power of 50% and ends when theinput power is raised to 60%. Therefore, if low input power is alwaysused, then a flicker phenomenon is likely to occur. In words, lowerpower input is requisite in order to assure the light amount gain of thelamp at 1.6, and this gives rise to a problem of occurrence of a flickerphenomenon at lower input power. Such a problem as just described ishereinafter referred to as flicker phenomenon problem.

Further, while, for example, in order to keep the luminance orbrightness of an image on the screen 34 fixed, it is necessary to adjustthe amount of light to be emitted from the lamp, a method of adjustingthe electric power amount of the light source is available as a methodfor the light amount adjustment. Where the electric power amount of thelight source is adjusted, generally the adjustment is carried outbetween maximum power and approximately one half the maximum power. Inparticular, where the maximum value and the minimum value of theadjustment range of the light amount are represented by 100% and 0%,respectively, the adjustment range is given by 50% to 100%. For example,the adjustment range for such lamps as illustrated in FIG. 3 is a rangebetween 2.1 and 4.2 kW for the lamp A; another range between 1.5 and 3.0kW for the lamp B; and a further range between 1.0 and 2.0 kW for thelamp C. Therefore, the lamp A, lamp B and lamp C may not emit light withpower lower than 2.1 kW, 1.5 kW and 1.0 kW, respectively. In otherwords, there is a problem that each of the lamp A, lamp B and lamp C maynot emit light of a brightness corresponding to power outside theadjustment range from 50% to 100%. Further, in addition to the method ofadjusting the power amount of the light source, also a method ofadjusting the light amount by opening/closing of an iris is known.However, although addition of an optical iris mechanism theoreticallymakes it possible to set the adjustment range of the light amount to arange from 0% to 100%, since the optical iris mechanism is newlymounted, it gives rise to a new problem that some physical restrictionis caused by parts to be added and a rise of the cost is invited.

Therefore, in the information processing system of FIG. 1 to which thepresent invention is applied, the projector 33 which can solve thevarious problems described above is installed in each screening place22. In other words, the projector 33 is a form of a projector to whichthe present invention is applied. An example of a configuration of theprojector 33 is shown in FIG. 4.

Referring to FIG. 4, the projector 33 includes a central processing unit(CPU) 51, a memory 52, an inputting/outputting section 53, aninput/output (I/O) section 54, a motor drive 55, an encoder 56, a motor57, a lamp house 58, a lamp power supply section 59, a light amountsensor 60, an input/output interface 61, a communication section 62 anda drive 63.

The CPU 51 executes various processes in accordance with programs and soforth recorded in the memory 52. The memory 52 suitably stores also dataand so forth necessary for the CPU 51 to execute various processes.

Also the inputting/outputting section 53, I/O section 54 andinput/output interface 61 are connected to the CPU 51.

The inputting/outputting section 53 includes an inputting section 71formed, for example, from a touch panel for being operated by a usersuch as an operator, and a display section 72 formed from a display unitand so forth for displaying the substance of such operation and soforth.

The I/O section 54 repeats various kinds of information between the CPU51 and the motor drive 55, encoder 56, lamp power supply section 59 orlight amount sensor 60.

The lamp house 58 for receiving a lamp 83 mounted thereon has anelectric power section 81 provided for movement in three directionsalong X, Y and Z axes illustrated in FIG. 4. The motor 57 and theencoder 56 which generates a pulse in response to the rotational angleof a movable rotary shaft of the electric power section 81 aremechanically connected to the movable rotary shaft. An ellipticreflecting mirror 82 for suppressing spreading of light from the lamp 83to irradiate the light to a remote plate is provided on the lamp house58 in addition to the electric power section 81 and the lamp 83.

The CPU 51 controls the motor drive 55 through the I/O section 54 todrive the motor 57. When the motor 57 is driven, the electric powersection 81 is moved in the three axis directions in FIG. 4 so that alsothe lamp 83 mounted on the lamp house 58 is moved. At this time, a pulsesignal is generated by the encoder 56 in response to the amount ofmovement of the electric power section 81 and read by the CPU 51 throughthe I/O section 54. Consequently, the CPU 51 can acquire informationregarding the position of the lamp 83.

The light amount sensor 60 is provided at a position at which it canmeasure the amount of light emitted from the lamp 83 and detects theamount of light. The CPU 51 controls the light amount sensor 60 throughthe I/O section 54 to acquire information regarding the amount of lightmeasured by the light amount sensor 60.

The lamp power supply section 59 is a power supply which can drive aplurality of different kinds of lamps 83. The lamp power supply section59 provides appropriate driving power to the lamp 83 mounted on the lamphouse 58 under the control of the CPU 51 through the I/O section 54.

The communication section 62 and the drive 63 are connected to theinput/output interface 61. The communication section 62 controlscommunication carried out with a different apparatus such as the screenmanagement apparatus 31 or material server 32 shown in FIG. 1. The formof communication in this instance is not limited particularly, but maybe wired communication or wireless communication. Further, thecommunication may be carried out through direct connection or carriedout through a network including the Internet.

Further, the communication section 62 may acquire a program from theoutside under such communication control and store the acquired programinto the memory 52.

The drive 63 drives, when a removable medium 64 such as a magnetic disk,an optical disk, a magneto-optical disk or a semiconductor memory isloaded therein, the removable medium 64 to acquire a program, data andso forth recorded on the removable medium 64. The acquired program anddata are transferred to and stored into the memory 52 as occasiondemands.

Incidentally, the lamp house 58 shown in FIG. 4 has such an internalconfiguration as, for example, shown in FIG. 5.

Referring to FIG. 5, the lamp 83 serving as a light source is mounted onthe lamp house 58 in such a manner as to be secured to the electricpower section 81. Consequently, if the electric power section 81 ismoved in three directions indicated by X₈₁, Y₈₁ and Z₈₁ in FIG. 5, thenthe lamp 83 is moved in the three axial directions of the X, Y and Zaxes in FIG. 5 corresponding to the directions of the movement of theelectric power section 81.

In the present embodiment, the lamp 83 has, for example, such a shape asseen in FIG. 6. In the present embodiment, any lamp which may possiblybe incorporated as the lamp 83 in the projector 33 (exchangeability) hasa shape same as that shown in FIG. 6. It is to be noted, however, thatsuch lamps may possibly have various lamp sizes. Further, the shape ofthe lamp 83 shown in FIG. 6 is a mere example but is not limitedparticularly only if it allows the lamp 83 to be mounted on the lamphouse 58. In other words, the lamp house 58 in the present embodimentcasually has a structure which allows the lamp 83 of the shape shown inFIG. 6 to be mounted on the lamp house 58.

Referring back to FIG. 5, the elliptic reflecting mirror 82 is, forexample, an elliptic reflecting mirror or elliptic mirror having anelliptic reflecting face which changes the advancing direction of alight beam from the lamp 83 and condenses light from a bright spot ofthe lamp 83 having a focus B as a first focus on the major axis of suchan ellipse A as seen in FIG. 5 on another focus C as a second focuswhich is on the major axis mentioned above.

FIG. 7 shows details of the ellipse A shown in FIG. 5. In other words,FIG. 7 illustrates a manner of reflection of light by the ellipticreflecting mirror 82 with respect to the position of the lamp 83 servingas a light source.

Referring to FIG. 7, in the example shown, light outgoing from the focusB is condensed at the focus C. Further, as indicated by shorter brokenlines in FIG. 7, light outgoing from the position of a point E iscondensed at a point G, and as indicated by longer broken lines in FIG.7, light outgoing from the position of a point F is condensed at a pointH.

In particular, if it is assumed that the elliptic reflecting mirror 82is designed such that, when the light source, that is, the bright pointof the lamp 83, is positioned at the focus B, if light is condensed atthe focus C, then a maximum luminance is obtained, that is, a maximumluminance is approached, then if the position of the bright point of thelamp 83 is moved to the “+” side or the “−” side along the Z directionin FIG. 7, then the light condensing position varies and is displacedfrom the focus C at which the maximum luminance is obtained. Therefore,the light utilization efficiency drops. In particular, for example, ifthe position of the bright point of the lamp 83 positioned at the focusB is moved to the “+” side in the Z direction in FIG. 7 to move theposition of the bright point of the lamp 83 to the point E, then lightoutgoing from the point E is condensed at a point G. Therefore, theutilization efficiency of light emitted from the lamp 83 drops.Similarly, if the position of the bright point of the lamp 83 positionedat the focus B is moved to the “−” side in the Z direction, then lightoutgoing from the point F is condensed at the point H. Therefore, theutilization efficiency of the light emitted from the lamp 83 dropssimilarly.

In other words, by displacing the light condensing positionintentionally from the position at which a maximum luminance isobtained, the utilization efficiency of light emitted from the lamp 83can be dropped similarly. Consequently, for example, also outside theadjustment range of 50% to 100% in FIG. 3 described hereinabove, lightof brightness corresponding to power outside the range can be emitted bydisplacing the position of the lamp 83 to intentionally drop theutilization efficiency of light. In particular, in the example of FIG.3, light of brightness corresponding to electric power lower than 2.1 kWfor the lamp A, lower than 1.5 kW for the lamp B and lower than 1.0 kWfor the lamp C can be emitted.

It is to be noted that, while, in the example described above, theposition of the bright point of the lamp 83 serving as a light source ismoved in the Z axis direction, even if the position of the bright pointof the lamp 83 is moved in the X direction, Y direction, XZ direction,XY direction or the like, the brightness can be changed. The essentialpoint is that only it is necessary for the condensing point of lightfrom the light source to be displaced from the focus C at which amaximum luminance is obtained, and the light source may be moved in anarbitrary direction.

FIG. 8 is a graph illustrating a relationship between the amount ofmovement of the lamp 83 and the relative illuminance when the lamp 83 ismoved in the three directions of the X, Y and Z axes.

Referring to FIG. 8, the axis of abscissa indicates the amount ofmovement of the lamp 83 and the axis of ordinate indicates the relativeilluminance when the lamp 83 is moved in the axial directions of the X,Y and Z axes. From FIG. 8, it can be seen that, where the amount ofmovement of the lamp 83 is equal in the axial directions of the X, Y andZ axes, the utilization efficiency of light is comparatively high withthe axis with regard to which the relative illuminance has acomparatively high value. Further, FIG. 8 indicates curves indicative ofthe value of the relative illuminance when the bright point of the lamp83 is moved in the three directions of the X, Y and Z. Among the curves,the curve when the lamp 83 is moved in the X direction is denoted by x;the curve when the lamp 83 is moved in the Y direction by y; and thecurve when the lamp 83 is moved in the Z direction by z.

In FIG. 8, the position of a vertical line at the center indicates theposition of the lamp 83 when the lamp movement amount is zero, that is,indicates the focus B at which the lamp 83 is positioned and light fromthe lamp 83 can be condensed at the focus C at which a maximum luminanceis obtained. Accordingly, in this instance, since the utilizationefficiency of light emitted from the lamp 83 is highest, the relativeilluminance exhibits a maximum value with regard to all of the curves x,y and z.

In FIG. 8, if the lamp movement amount increases, that is, if theposition of the lamp 83 is spaced away from the focus B, then therelative illuminance gradually decreases. However, the curve x is moremoderate than the curve z, and the curve y is more moderate than thecurve x.

In other words, where an equal lamp movement amount is considered, therelative illuminance increases in the order of the curve y, curve x andcurve z. Therefore, if the lamp 83 is moved, for example, in the Zdirection, then the illuminance can be decreased by a greater amountthan where the lamp 83 is moved by the same lamp movement amount in theX or Y direction. In other words, if the lamp 83 is moved in the Zdirection from among the three directions of the X, Y and Z axes, thenthe utilization efficiency of light can be decreased most efficientlywith respect to the amount of movement of the lamp 83.

In this manner, in the present embodiment, the adjustment range of thelight amount can be expanded by moving the lamp 83 merely in any one ofthe three directions of the X, Y and Z axes without providing anadditional part such as an iris mechanism to the optical system.Consequently, a physical restriction by an additional part or the likewhen an optical iris mechanism is attached newly can be eliminated, andincrease of the cost can be suppressed to a minimum level. Further,since an existing mechanism having a function of moving the lamp 83 inthe three directions of the X, Y and Z axes can be utilized, thefunctions mentioned can be implemented very readily.

It is to be noted that, in the present embodiment, by what amount thelamp 83 should be moved in any of the three directions of the X, Y and Zaxes is determined depending upon by what amount the utilizationefficiency of light should be dropped.

Incidentally, light emitted from the lamp 83 is reflected by theelliptic reflecting mirror 82 as seen in FIG. 9 and emitted, through anilluminating system unit 92 which uniformizes the light, to a liquidcrystal light valve apparatus 93 which modulates the light based ondigital data of a movie or material to be screened from the materialserver 32. Then, image data obtained by emitting the light to the liquidcrystal light valve apparatus 93 is projected to the screen 34 through aprojection lens 94. Consequently, an image corresponding to the digitaldata provided from the material server 32 is projected from theprojector 33 to the screen 34. As a result, the movie is screened on thescreen 34.

In FIG. 9, a lamp position adjustment mechanism 91 is composed of, forexample, the CPU 51, I/O section 54, motor drive 55, encoder 56 andmotor 57 shown in FIG. 4 and adjusts the position of the lamp 83. Moreparticularly, the lamp position adjustment mechanism 91 moves theposition of the lamp 83 in the three directions of the X, Y and Z axesin FIG. 9 so that the bright point of the lamp 83 serving as a lightsource is displaced from the first focus of the elliptic reflectingmirror 82, for example, from the focus B shown in FIG. 5, to decreasethe effective light amount of the lamp 83, that is, to displace thecondensing point of light from the focus C shown in FIG. 5. In otherwords, the lamp position adjustment mechanism 91 moves the bright pointof the lamp 83 in a direction of the optical axis of the ellipticreflecting mirror 82 or in a direction different from the optical axisof the elliptic reflecting mirror 82.

The liquid crystal light valve apparatus 93 is an image display devicesuch as a liquid crystal light valve apparatus of fixed pixels used fora projector of the light valve type. The image display device may be aliquid crystal panel of the reflection type such as a liquid crystalvalve apparatus or a device which can use light emitted from the lamp 83to display an image corresponding to digital data from the materialserver 32 such as a mirror device of the reflection type such as adigital mirror device (DMD).

The liquid crystal light valve apparatus 93 modulates light, that is,reflected light, from the lamp 83 reflected by the elliptic reflectingmirror 82 with digital data from the material server 32 to convert thelight or reflected light into image light.

The projection lens 94 is used to project the image light from theliquid crystal light valve apparatus 93 to the screen 34 and is providedbetween the screen 34 and the liquid crystal light valve apparatus 93.The image light from the liquid crystal light valve apparatus 93 isexpanded by the projection lens 94 and emitted to the screen 34.

It is to be noted that the projection lens 94 is formed as a group ofone or more lenses having a zooming function. In this instance, whilethe magnitude of an image corresponding to the image light on the screen34 can be changed by changing the position of the projection lens 94,when the zooming condition is changed, the light of amount sometimeschanges to make the luminance of the image on the screen 34 excessivelybright. The situation that the image becomes excessively bright can beprevented by adjusting the position of the lamp 83 to lower theutilization efficiency of light.

Further, while the elliptic reflecting mirror 82 having a reflectingface in the form of an elliptic face is described in the description ofthe present embodiment, it is possible to use a parabolic mirror havinga reflecting face in the form of a parabolic face in place of theelliptic reflecting mirror 82. In this instance, since reflection lightfrom the parabolic mirror is parallel light, a luminance variation maynot be obtained by movement of the lamp 83 in the Z axis direction.Therefore, the lamp 83 is moved in the X direction or the Y direction toobtain an effect similar to that obtained by the elliptic reflectingmirror 82.

Further, though not shown, a spherical mirror may be provided at aposition confronting with the elliptic reflecting mirror 82. Inparticular, this spherical mirror may be provided to collect overflowinglight to raise the efficiency of light emission of the lamp 83.

Now, an example of a process executed when a flicker phenomenon in a lowinput state occurs during execution of a calibration mode from amongvarious processes executed by the projector 33 having such aconfiguration as described above is described with reference to a flowchart of FIG. 10. It is to be noted that the process mentioned ishereinafter referred to as flicker detection process.

It is to be noted that, while, in the projector 33, the lamp input isnormally set to 50 to 100%, the CPU 51 executes the flicker detectionprocess of FIG. 10, for example, when a calibration mode is carried out.

At step S11, the CPU 51 controls the lamp power supply section 59through the I/O section 54 to set the power lower limit value, forexample, to 50%. For example, information of the power lower limit valueset to 50 or the like is stored into the memory 52. Consequently, thelamp 83 mounted on the lamp house 58 is turned on to emit light with thedriving power of 50% supplied thereto from the lamp power supply section59.

At step S12, the CPU 51 decides whether or not the currently set powerlower limit value is lower than 100%. If it is decided that the powerlower limit value is 100%, then the CPU 51 controls the display section72 to display an alarm for lamp exchange. Thereafter, the flickerdetection process is ended.

In particular, if it is decided that the power lower limit value is100%, then the power lower limit value may not be raised any more andthe flicker phenomenon may not be suppressed any more. Therefore, analarm for urging the user to exchange the lamp 83 is displayed on thedisplay section 72 so that the user may exchange the lamp 83.

In this manner, a flicker phenomenon is a significant rough estimate forlamp exchange, and if a flicker phenomenon is detected while the powerlower limit value is set to 100%, then since an alarm for urging theuser to exchange the lamp is outputted, it is possible to notify theuser of an appropriate lamp exchanging timing so that otherwise possiblefailure by bursting of the lamp by normal use can be prevented.

On the other hand, if it is decided at step S12 that the power lowerlimit value is lower than 100%, then the CPU 51 sets a counter N, forexample, to 1 to initialize the counter N at step S14.

Then at step S15, the CPU 51 reads in a light amount sensor valuemeasured by the light amount sensor 60 through the I/O section 54. Thenat step S16, the CPU 51 integrates data corresponding to the lightamount sensor value thus read in.

At step S17, the CPU 51 decides whether or not the value of the counterN is equal to or higher than a predetermined number such as, forexample, 10. If it is decided at step S17 that the value of the counterN is lower than 10, then the CPU 51 increments the value of the counterN by one at step S18. Thereafter, the processing returns to step S15.

Consequently, the processes at steps S15 to S18 are repeated until afterit is decided at step S17 that the value of the counter N becomes equalto or higher than 10. In other words, the processes at steps S15 to S18are repeated 10 times at fixed intervals until the value of the counterN becomes equal to or higher than 10 which is the predetermined numberof times. Therefore, 10 integrated values are determined by the processat step S16.

After a predetermined number of integrated values such as 10 integratedvalues are determined, the CPU 51 calculates a variation value based onthe integrated values at step S19. This variation value is calculated,for example, in accordance with the following expression (1):

variation value=(maximum value of integrated value−minimum value ofintegrated value)/average value of integrated value   (1)

In particular, in the expression (1), maximum and minimum integratedvalues are selected from among, for example, 10 integrated values, andan average value of the 10 integrated values is calculated. Further, thedifference between the selected maximum and minimum integrated values isdivided by the calculated average value to calculate the variationvalue.

At step S20, the CPU 51 decides whether or not the calculated variationvalue is equal to or lower than a specified value determined in advance.

Here, the specified value is determined in advance, for example, by amanufacturer of the projector 33 or the like. In particular, accordingto the specification, a reference or threshold value for decidingoccurrence of a flicker is determined, and if the calculated variationvalue exceeds the reference, then it is decided that a flickerphenomenon currently occurs.

If it is decided at step S20 that the variation value is higher than thespecified value, then the CPU 51 increases the power lower limit valueby 10% at step S21. Then at step S22, the CPU 51 decides whether or nota predetermined interval of time such as one minute, elapses. Then, thedeciding process at step S22 is repeated until after it is decided atstep S22 that the predetermined interval of time elapses.

In particular, if it is decided that the variation value is higher thanthe specified value, then this indicates that a flicker phenomenon iscurrently proceeding. Since a flicker phenomenon has a nature that itstops if the power of the lamp 83 is raised as described hereinabove,the power lower limit value is changed from 50% to 60% to raise thepower of the lamp 83 for 10%.

If it is decided at step S22 that the predetermined interval of timesuch as one minute elapses, then the processing returns to step S12 torepeat the processes described above.

Then, the processes at steps S12 to S22 described above are repeateduntil after it is decided at step S22 that the predetermined interval oftime such as one minute elapses. In particular, while the power lowerlimit value is increased successively by 10% like 60%, 70%, 80% and 90%,the variation value of the amount of light emitted from the lamp 83which is turned on to emit light is successively calculated, andcomparison between the calculated variation value and the specifiedvalue is carried out successively.

If it is decided at step S20 that the variation value is equal to orlower than the specified value, then the CPU 51 sets the power lowerlimit value to a power lower limit value for the case wherein thevariation value is equal to or lower than the specified value, forexample, to 90% at step S23. Thereafter, the flicker detection processis ended.

As described above, when a flicker phenomenon which occurs upon lowinput power driving is detected, the power lower limit value or lampinput value is successively increased until the flicker phenomenondisappears. By this, a flicker which occurs upon low input power drivingcan be suppressed, and a sufficient lamp life upon low input powerdriving can be assured. In other words, the flicker phenomenon problemcan be solved.

Further, to extend the lamp life upon low input power driving against aflicker provides also an effect that the lamp life is substantiallyextended. Furthermore, a flicker can be used as a significant roughestimate for lamp exchange, and to issue an alarm for urging the userfor lamp exchange upon detection of a flicker with a 100% power input issignificant from the point of view of prevention of bursting of the lampby excessive use.

Now, a process of moving the lamp 83, which is executed when theadjustment range of the amount of light emitted from the lamp 83 isexpanded, from among the processes executed by the projector 33 havingthe configuration described hereinabove is described with reference toFIG. 11. It is to be noted that the process mentioned is hereinafterreferred to as lamp position adjustment process.

As described hereinabove, it is prescribed that, when the size of animage to be projected on the screen 34 of the screening place 22 ischanged over from the scope size to the vista size, the luminance of theimage to be projected on the screen 34 is kept fixed between the twodifferent angles of field, and in order to implement this, it isnecessary to assure the light amount gain of the lamp 83 at 1.6. The CPU51 thus executes the lamp position adjustment process of FIG. 11, forexample, if it is necessary to keep the luminance of an image to beprojected on the screen 34 whose image size is changed over to the vistasize at a desired value after the flicker detection process of FIG. 10comes to an end.

At step S31, the CPU 51 reads in a light amount sensor value measured bythe light amount sensor 60 through the I/O section 54 and decideswhether or not the light emitted from the lamp 83 is excessively bright.In particular, the CPU 51 decides whether or not the light amount sensorvalue from the light amount sensor 60 for detecting, for example, theamount of light emitted to the screen 34 after changeover to the vistasize, is equal to or higher than a value demanded for the vista size todecide whether or not the light from the lamp 83 is excessively bright.

If it is decided at step S31 that the light emitted from the lamp 83 isnot excessively bright, that is, that the light has a desired level ofbrightness, then since there is no necessity to adjust the position ofthe lamp 83, processes at steps S32 to S35 are skipped and the lampposition adjustment process is ended immediately.

On the other hand, if it is decided at step S31 that the light emittedfrom the lamp 83 is excessively bright, then the CPU 51 decides at stepS32 whether or not the position of the lamp 83 is within a limit rangewithin which it is movable. If it is decided at step S32 that theposition of the lamp 83 is outside the limit range, then since the lamp83 may not be moved any more, the lamp position adjustment process isended.

On the other hand, if it is decided at step S32 that the position of thelamp 83 is within the limit range, then since it is possible to move thelamp 83, the CPU 51 acquires a light amount sensor value and positiondata from the light amount sensor 60 and the encoder 56, respectively,through the I/O section 54.

At step S34, the CPU 51 controls the motor 57 through the I/O section 54and the motor drive 55 based on the light amount sensor value andposition data acquired as described above to drive the electric powersection 81 thereby to move the lamp 83 in one of the three directions ofthe X, Y and Z axes.

It is to be noted that, as a method of shifting the lamp 83 to adjustthe position of the lamp 83, for example, an optimum value of theposition to which the lamp 83 is to be shifted is recognized by theencoder 56, and every time the angle of field is changed over, theposition of the lamp 83 is changed over based on the recognized optimumvalue so that the luminance of the image to be projected on the screen34 can be kept fixed.

Further, in the present embodiment, the electric power section 81 has amovable amount with which the lamp gain of 1.6 can be implemented onlyby movement of the position of the lamp 83 while the input is kept at100%.

At step S35, the CPU 51 decides based on the light amount sensor valuefrom the light amount sensor 60 after the movement of the position ofthe lamp 83 whether or not the amount of light emitted from the lamp 83is lower than the desired luminance. If it is decided at step S35 thatthe amount of light emitted from the lamp 83 still remains equal to orhigher than, for example, the value requisite for the vista size and theluminance on the screen 34 is equal to or higher than the desiredluminance, then the processing returns to step S32. Consequently, theprocesses at steps S32 to S35 described above are repeated until afterit is decided at step S35 that the luminance on the screen 34 is lowerthan the desired luminance.

On the other hand, if it is decided at step S35 that the luminance onthe screen 34 is lower than the desired luminance, then the luminance isequal to or lower than the value demanded, for example, for the vistasize, and since the luminance of the image projected on the screen 34can be kept fixed, the lamp position adjustment process is ended.

As described above, the adjustment range of the light amount can beexpanded only by moving the lamp 83 in any one of the three directionsof the X, Y and Z axes to adjust the position of the lamp 83 withoutproviding an additional part of an iris mechanism and so forth on theoptical system. In other words, by moving the lamp 83 in any one of thethree directions of the X, Y and Z axes to positively degrease theeffective light amount of the liquid crystal light valve apparatus 93,the adjustment range of the peak luminance can be expanded withoutdamaging the gradation of the liquid crystal light valve apparatus 93.In other words, the lamp adjustment range problem can be solved.

On the other hand, for example, if the angle of field or aspect ratio ofthe movie is changed, then in order to keep the luminance of the imageon the screen 34 fixed, it becomes necessary to adjust the amount oflight to be emitted from the lamp 83. In this instance, after theflicker detection process of FIG. 10 is executed, the lamp positionadjustment process of FIG. 11 is carried out to displace the position ofthe lamp 83 in a direction in which the image projected on the screen 34becomes dark. By this, the luminance of the image can be kept fixedreadily. Consequently, the flicker phenomenon problem and the lampadjustment range problem can be solved simultaneously. For example, ifadjustment of the light output of the lamp 83 within the range from 100%to approximately 50% by the flicker detection process of FIG. 10 iscarried out additionally, then a range of the luminance from 100% toapproximately 30% of the maximum luminance can be made the adjustmentrange.

Further, while the lamp 83 may have any lamp size from among variouslamp sizes as described above, since the adjustment range of the lightamount can be expanded, the number of types of the lamp 83 can bereduced.

It is to be noted that, while, in the embodiment described above, theadjustment range of the light amount can be expanded by adjusting theposition of the lamp 83, similar effects can be anticipated also bymoving or rotating the elliptic reflecting mirror 82 or the illuminatingsystem unit 92 in place of the movement of the lamp 83.

Further, in the projector 33 of FIG. 4, it is possible to use anexternal personal computer or like apparatus to input data or displaydata without providing the inputting/outputting section 53 including theinputting section 71 and the display section 72.

Further, while, in the embodiment described above, changeover of theangle of field according to the DCI Spec is described, also changeoverof the angle of field according to other standards can be appliedeffectively where screening involves changeover of the angle of field.

It is to be noted that, while the series of processes described abovecan be executed by hardware, it may otherwise be executed by software.Where the series of processes is executed by software, a program whichconstructs the software is installed from a recording medium into acomputer incorporated in hardware for exclusive use or, for example, apersonal computer for universal use which can execute various functionsby installing various programs.

The recording medium is formed from the removable medium 64 shown inFIG. 4 which may be a magnetic disc (including a flexible disc), anoptical disc (including a CD-ROM (Compact Disc-Read Only Memory) and aDVD (Digital Versatile Disc)), or a magneto-optical disc (including anMD (MINI DISC) (Registered Trademark of Sony Corporation), or asemiconductor memory which has the program recorded thereon or thereinand is distributed to provide the program to a user separately from acomputer. Else, the recording medium is formed as a ROM, a recordingsection or the like in which the program is recorded and which isprovided to a user in a state wherein the program is incorporated in acomputer in advance.

Further, the program for causing the series of processes describedhereinabove to be executed may be installed into a computer through aninterface such as a router or a modem and further through a wired orwireless communication medium such as a local area network, the Internetor a digital satellite broadcast as occasion demands.

It is to be noted that, in the present specification, the steps whichdescribe the program recorded in a recording medium may be but need notnecessarily be processed in a time series in the order as described, andinclude processes which are executed in parallel or individually withoutbeing processed in a time series.

Further, in the present specification, the term “system” is used torepresent an entire apparatus composed of a plurality of apparatus.

While a preferred embodiment of the present invention has been describedusing specific terms, such description is for illustrative purposesonly, and it is to be understood that changes and variations may be madewithout departing from the spirit or scope of the following claims.

1. A projector for projecting an image to a screen, comprising: a lampconfigured to emit light; an elliptic reflecting mirror configured toreflect and condense the light from said lamp; a sensor configured todetect the amount of the light reflected and condensed by said ellipticreflecting mirror; a lamp power supply configured to supply power tosaid lamp to drive said lamp; and a control circuit configured tosuccessively increase the power to be supplied from said lamp powersupply to said lamp until after a variation value of the amount of thereflected light detected by said sensor becomes equal to or lower than apredetermined threshold value.
 2. The projector according to claim 1,further comprising a position adjustment mechanism configured to adjustthe position of said lamp so that the bright point of said lamp isdisplaced from a first focus of said elliptic reflecting mirror.
 3. Theprojector according to claim 2, wherein said position adjustmentmechanism adjusts the position of said lamp when the aspect ratio of theimage displayed on said screen changes.
 4. The projector according toclaim 2, wherein said position adjustment mechanism moves the brightpoint of said lamp along an optical axis of said elliptic reflectingmirror or along a direction different from the optical axis.
 5. Theprojector according to claim 1, further comprising a display sectionconfigured to display an alarm for urging for exchange of said lamp whenthe variation value exceeds the predetermined value while the powersupplied from said lamp power supply to said lamp has a maximum value.6. The projector according to claim 1, wherein the threshold value is aspecified value determined in advance.
 7. A control method for aprojector for projecting an image to a screen, the projector including alamp configured to emit light, an elliptic reflecting mirror configuredto reflect and condense the light from said lamp, a sensor configured todetect the amount of the light reflected and condensed by said ellipticreflecting mirror, a lamp power supply configured to supply power tosaid lamp to drive said lamp, and a control circuit configured tocontrol said lamp power supply, the control method comprising the step,executed by said control circuit, of: successively increasing the powerto be supplied from said lamp power supply to said lamp until after avariation value of the amount of the reflected light detected by saidsensor becomes equal to or lower than a predetermined threshold value.